This work is concerned with the isolation, purification and characterization of enzymes used by micro-organisms to degrade benzenoid compounds. In particular, various dioxygenases that cleave the benzene nucleus of gallic acid, and of homoprotocatechuic acid, are being isolated and purified from species of Pseudomonas and Bacillus. It is expected that the results of these studies will have some bearing upon theories of the evolutionary origins of catabolic pathways, and that the pure enzymes themselves may be suitable for investigations of dioxygenase mechanisms of action.